Does bernd know anything about digital signal filtering?
I have some professional signal-processing software, it has all tools for filtering and analysis, and I have a simple case of noise. At least I think it is simple, since I can see the repeating pattern, and I know what is signal and what is not. What I don't have is the education to design a filter which would work. I messed around with the tool, it has a dozen different filters (low pass, two band, three band, three band with a notch, infinite impulse response, some named filters), and each has many settings. I think I need a rather low frequency filter (50hz?), since the source is likely power supply, but the tutorial I tried for that case just gave me garbage, and didn't explain much.
Bernd
Thu, 27 Feb 2025 17:09:15 GMT
No. 25524085
>>25524130
>>25524067
What are you planning on using the signal for exactly? How precise does it need to be?
Bernd
Thu, 27 Feb 2025 17:16:41 GMT
No. 25524126
>>25524170
>>25524067
>source is likely power supply
Get a better power supply?
Bernd
Thu, 27 Feb 2025 17:16:59 GMT
No. 25524127
>>25524166
just make a 180 phase-shifted copy the sum it with the original
nah?
Bernd
Thu, 27 Feb 2025 17:17:14 GMT
No. 25524130
>>25524160
>>25525505
>>25524085
This specific recording is an example of noise, my signal here is in the amplitude and auc of the peak. This one will work without filtering. But I also have other recordings where I have random downward peaks much like those ones but about 10 times smaller.
Bernd
Thu, 27 Feb 2025 17:18:05 GMT
No. 25524133
>>25524162
Do a frequency analysis thingy? Not just a recording.
Bernd
Thu, 27 Feb 2025 17:22:02 GMT
No. 25524160
>>25524130
I was asking because if you're in an academic context, you wouldn't typically filter the noise unless explicitly asked to do so.
You can apply a frequency filter quite easily in Audacity if you need to. Just play around with the values until you get something that looks good if you don't feel like calculating stuff.
https://manual.audacityteam.org/man/low_pass_filter.html
Bernd
Thu, 27 Feb 2025 17:22:10 GMT
No. 25524162
>>25524168
>>25524133
I did fast fourier transform but I dont understand the results. Its just a collection of peaks with amplitudes decreasing exponentially, but none seem to be much larger than others. I think maybe its because my recordings are rather short? Or its harmonics? Whatever that is. I can concatenate short ones into long ones but I didnt do it yet.
Bernd
Thu, 27 Feb 2025 17:23:09 GMT
No. 25524166
>>25524176
>>25524127
How do I shift the phase of the noise tho?
Bernd
Thu, 27 Feb 2025 17:23:24 GMT
No. 25524168
>>25524200
>>25524162
>peaks with amplitudes decreasing exponentially
You've got harmonics, it's completely normal. How much noise is there on the fourier transform?
Bernd
Thu, 27 Feb 2025 17:24:07 GMT
No. 25524170
>>25524126
I tried all kinds of grounding and its much better than with no grounding, but I still have the baseline noise with essential equipment
Bernd
Thu, 27 Feb 2025 17:25:19 GMT
No. 25524176
>>25524211
>>25524166
ach, sorry, what i described needs signal to be captured at 0 and 180 at the same time from the source
Bernd
Thu, 27 Feb 2025 17:27:42 GMT
No. 25524189
do a fourier transform and remove all the low frequencies manually
Bernd
Thu, 27 Feb 2025 17:29:19 GMT
No. 25524200
>>25524168
Idk, I didnt see a peak that would be obvious. I only know that its this repeating shape:
Its periodic and vaguely sine-like, so its not too complex. But its close to my signal in frequency as I understand it? Since I have like 8 of it per my time window, and 2 of the signal per the same window. I also have very high frequency sine noise on all of it if you really zoom in, but it doesnt bother me much.
Bernd
Thu, 27 Feb 2025 17:30:34 GMT
No. 25524208
you need to view the signal in the frequency domain the pic you posted is in time domain. if it's noise from the power supply try a notch filter at 50Hz or 60Hz, whichever your cunt uses.
Bernd
Thu, 27 Feb 2025 17:31:03 GMT
No. 25524211
>>25524213
>>25524176
Hmmm. I dont know how to do that. It's a DC circuit with square pulses, going through a biological object.
Bernd
Thu, 27 Feb 2025 17:31:34 GMT
No. 25524213
>>25524216
>>25524211
What? Are you working with neurons?
Bernd
Thu, 27 Feb 2025 17:32:06 GMT
No. 25524218
he is zapping his own balls
Bernd
Thu, 27 Feb 2025 17:32:07 GMT
No. 25524219
>>25524258
>>25524266
btw can op just do dynamic range compression in his settis?
like picrel example
Bernd
Thu, 27 Feb 2025 17:32:22 GMT
No. 25524223
>>25524234
>>25524216
Are you sure its not the neurons then? I heard neurons can make repeating patterns
Bernd
Thu, 27 Feb 2025 17:34:09 GMT
No. 25524234
>>25524244
>>25524223
No, no, its very rigid noise, nothing in biological world has periodicity of exactly whatever this Hz is, across both time in recordings and individuals
Bernd
Thu, 27 Feb 2025 17:36:38 GMT
No. 25524244
>>25524246
>>25524277
>>25524234
If its 50 hz exactly then its most likely electrical interference from the grid.
Bernd
Thu, 27 Feb 2025 17:39:30 GMT
No. 25524258
>>25524219
>dynamic range compressio
Hmmm interdasting. Never thought of processing sound in matlab, but its the first link in search
Bernd
Thu, 27 Feb 2025 17:41:46 GMT
No. 25524266
>>25524300
>>25524811
>>25524219
I dont think that's the power supply or the lights.
>>25524244
The problem is I dont understand the FFT output. it gives me many many peaks and the first highest peak is at 33.33.. Hz, and then exponentially decreasing in amplitude peaks at equal intervals. The FFT tool also has like 6 modes of output, and thirty settings, so I dont know what I'm doing with it.
Bernd
Thu, 27 Feb 2025 17:43:09 GMT
No. 25524284
>>25524291
>>25524277
try to remove all the big frequencies and leave the normal ones alone
Bernd
Thu, 27 Feb 2025 17:43:49 GMT
No. 25524291
>>25524355
>>25524284
How? High pass filter with low setting?
Bernd
Thu, 27 Feb 2025 17:45:42 GMT
No. 25524309
>>25524298
Hmmmm I need my cumpooter, give me a sex
Bernd
Thu, 27 Feb 2025 17:47:05 GMT
No. 25524319
>>25524277
The big peaks are what you're looking to keep, it's the fundamental and it's the various harmonics. It's the strongest parts of your signal, and considering it's harmonics are at equal intervals, it's precisely the signal you're looking to keep.
You need to filter out everything that is outside of those big peaks, if there's noise you should notice some smaller, insignificant peaks that need to be dealt with. Probably.
Bernd
Thu, 27 Feb 2025 17:48:58 GMT
No. 25524333
>>25524484
generally for an FFT you want a long sampling duration and a sampling frequency of at least 2x higher than the fastest moving signal but since this is biological it's not very fast.
Bernd
Thu, 27 Feb 2025 17:51:05 GMT
No. 25524355
>>25524552
>>25524291
when you see the frequency domain cant you select with your mouse a peak and delete it?
Bernd
Thu, 27 Feb 2025 18:07:49 GMT
No. 25524484
>>25524555
>>25524333
Ok, here's longer data and an FFT output in mode "real", and the highest peak is at "10"
Theres also modes complex, magnitude, magnitude squared, phase, scaled magnitude and scaled magnitude squared for FFT
Bernd
Thu, 27 Feb 2025 18:15:06 GMT
No. 25524552
>>25524879
>>25524355
Its just another wave. Maybe there is such a tool but I dont know which one it might be. If its a filter, here are the filter tools. Trying high pass filter but I dont know if that looks right, dont think it does. Filtered is blue, dashed is original
Bernd
Thu, 27 Feb 2025 18:15:14 GMT
No. 25524555
>>25524573
>>25524484
I find that noise very strange. The sudden rise and the exponential decay suggest something switching. The alternating sign is like a digital flip-flip thingy, but viewed through some capacity. I try to make a sketch.
Bernd
Thu, 27 Feb 2025 18:17:08 GMT
No. 25524573
>>25524618
>>25524555
The sharp peaks is my doing, it is a square pulse going through a resistor and a capacitor (in a way). The noise is the baseline, which should be flat (flatter than this)
Bernd
Thu, 27 Feb 2025 18:21:45 GMT
No. 25524618
>>25524682
>>25524573
Okay, that makes it more clear. Switch it off. What's the noise then? And the FFT?
>>25524618
This is another recording, very long, without my input, same kind of noise I think. It has largest peak at 50Hz and harmonics? at 100, 150, 200 etc. Must be power supply?
Bernd
Thu, 27 Feb 2025 18:30:06 GMT
No. 25524692
>>25524682
>200
well not 200 but still with a 50 hz step
Bernd
Thu, 27 Feb 2025 18:31:38 GMT
No. 25524712
>>25524682
So much more clear. It's not necessarily the power supply. Unless you shield everything, and properly, you'll pick up noise from all the surrounding equipment. Lamps, fans, monitors, computers, ovens, ACs, you name it.
Bernd
Thu, 27 Feb 2025 18:34:55 GMT
No. 25524736
>>25524762
>>25524682
ok that looks like 50hz noise and its odd harmonics (3x, 5x, etc). Try a notch filter at 50hz and 150hz since those are the biggest ones.
>>25524736
I think 50 hz works! I'm still not sure what all those settings mean or if it can be tweaked further, but the repeating shape is gone! Thanks bernds, the issue with FFT seems to be that my recordings were too short, just around one second, but I looked through the data and found a 30 seconds one, without square pulses, then FFT worked
Bernd
Thu, 27 Feb 2025 18:43:43 GMT
No. 25524789
>>25524868
EE is the most bernd tyre field
Bernd
Thu, 27 Feb 2025 18:44:51 GMT
No. 25524793
>>25524829
>>25524762
How about switching the digital signal back on? Are you still happy?
Bernd
Thu, 27 Feb 2025 18:48:41 GMT
No. 25524811
>>25524266
I think the 70Hz signal was your test pulse. It's always nice to include a schematic and description of the signals so there's no ambiguity.
Bernd
Thu, 27 Feb 2025 18:49:06 GMT
No. 25524813
>>25524856
>>25524762
what exactly is this system and whats teh signal you are interested in?
is this an audio signal?
bernd is an EE can maybe help, but other bernds seem to already figured out what you need
>>25524793
Hmmmm its better but still kinda ass? Strange
Bernd
Thu, 27 Feb 2025 18:52:48 GMT
No. 25524843
>>25524879
>>25524829
what options do you have for low pass filters?
the LP filter wiill smooth your signal and get rid of the sudden jolts
Bernd
Thu, 27 Feb 2025 18:53:25 GMT
No. 25524847
>>25524849
>>25524829
you could try averaging. white noise zeroes out and you're left with the main signal.
Bernd
Thu, 27 Feb 2025 18:53:51 GMT
No. 25524849
>>25524852
>>25524847
>you could try averaging
averaging filters are Low-pass filters
Bernd
Thu, 27 Feb 2025 18:54:38 GMT
No. 25524856
>>25524880
>>25524813
It's a DC circuit where there is an unknown complex "resistor" and unknown less complex "capacitor", and the idea is to describe those unknowns by subjecting them to whatever current of any shape you can think of
Bernd
Thu, 27 Feb 2025 18:56:02 GMT
No. 25524868
>>25524789
Yes, I'm hooooofing an autism
Bernd
Thu, 27 Feb 2025 18:57:21 GMT
No. 25524879
>>25524897
>>25524843
The menu on the right of pic here
>>25524552
Each option may or may not have sub-options
Bernd
Thu, 27 Feb 2025 18:57:21 GMT
No. 25524880
>>25524923
>>25524926
>>25524856
do you want to measure the resistance and capacitance?
do you create the input signal digitally?
a ramp signal or chirp signal is typically used to measure system functions
in your case system function should consist of the resistor and capacitor in series, right?
Bernd
Thu, 27 Feb 2025 18:58:57 GMT
No. 25524897
>>25524940
>>25524879
a normal FIR filter should be fine, try the Low-pass option for MPR filters or look in window filters
Bernd
Thu, 27 Feb 2025 19:00:38 GMT
No. 25524910
Fast fourier transform will get the job done.
Bernd
Thu, 27 Feb 2025 19:04:21 GMT
No. 25524923
>>25524880
What I mostly do is that I'm amplifying the activity of a living cell, and I record that activity and responses to my actions. Electrically its (very roughly) a sphere of insulator with typical specific capacitance, described by total capacitance, and this insulator is bridged by multiple types of resistors (different rules for each type) that are behaving simultaneously, giving me some total resistance. I control the current either manually or with high frequency feedback which allows me to set voltage in the system to where I want it by quickly altering the current against intrinsic unknown currents arising in the system
Bernd
Thu, 27 Feb 2025 19:04:40 GMT
No. 25524926
>>25524933
>>25524829
>ass?
>>25524880
>do you create the input signal digitally?
Maybe your square wave is square only in your heda? We've all seen plenty of ringing. And the filter works fine, but you have two sources of noise?
Bernd
Thu, 27 Feb 2025 19:06:15 GMT
No. 25524937
>>25524950
>>25524933
You want the red one, but you get the yellow.
Bernd
Thu, 27 Feb 2025 19:06:56 GMT
No. 25524940
>>25525022
>>25524897
You mean I should apply few filters one after another?
Bernd
Thu, 27 Feb 2025 19:08:00 GMT
No. 25524950
>>25524981
>>25524985
>>25524937
I assume I need an oscilloscope before my ADC to see that?
Bernd
Thu, 27 Feb 2025 19:08:04 GMT
No. 25524954
>>25524971
Do frequency transform to figure out what you need to filter out
Bernd
Thu, 27 Feb 2025 19:09:51 GMT
No. 25524971
>>25524954
>>25524682
Its power supply I guess. But maybe something else too
Bernd
Thu, 27 Feb 2025 19:12:01 GMT
No. 25524981
>>25524950
I mean, after DAC. Uhhhhhhhhh
Bernd
Thu, 27 Feb 2025 19:12:32 GMT
No. 25524985
>>25525013
>>25524950
Yes, an oscilloscope would be nice for jobs like this.
For giggles, and to test this ringing theory, you may try to decrease the drive of your digital output, it will lose the initial sharpness but it will decrease the ringing quite a bit.
Bernd
Thu, 27 Feb 2025 19:15:15 GMT
No. 25525008
>>25525021
>>25525229
>>25524857
>>25524852
an average filter sums over multiple samples of a signal and then outputs their average.
any instantaneous jiggle of the signal is supressed by the summing, which leads to LP characteristics.
see pic frequency response of average filters with different sizes
Bernd
Thu, 27 Feb 2025 19:16:10 GMT
No. 25525013
>>25525047
>>25524985
>decrease the drive
What does that mean? Sampling rate?
Bernd
Thu, 27 Feb 2025 19:17:08 GMT
No. 25525021
>>25525113
>>25525008
Why is it teethed like that?
Bernd
Thu, 27 Feb 2025 19:17:18 GMT
No. 25525022
>>25525067
>>25524940
>You mean I should apply few filters one after another?
since you care about the absolute voltage and only want to supress sudden changes in the signal you will need an low-pass filter
remove the other filters you dont need them
please show what options you have foe low pass filters and window filters
Bernd
Thu, 27 Feb 2025 19:19:42 GMT
No. 25525047
>>25525092
>>25525013
Dunno. I'm but a codemonkey. Digital gates has some resistors-like things which limits the current they will output to maintain the desired voltage level. More current, faster switching. Also, more current, much more ringing.
Sometimes you can set this in software on silly boards, like a raspberry pi pico.
If ringing is truly your problem, you'll have to tune you circuit. Or use cleaner signals.
>a ramp signal or chirp signal is typically used to measure system functions
Bernd
Thu, 27 Feb 2025 19:21:55 GMT
No. 25525067
>>25525132
>>25525022
Low pass window filter has 5 types to select from, Hanning, Parzen, Welch, Kaiser[1] and rectangular, end of first band, start of second band, and number of terms.
Bernd
Thu, 27 Feb 2025 19:24:23 GMT
No. 25525092
>>25525137
>>25525047
Well, I do need an oscilloscope I suppose, to verify the amplifier. It is supposedly a mature piece of rack tech, very niche and expensive, but you never know.
Bernd
Thu, 27 Feb 2025 19:26:12 GMT
No. 25525113
>>25525021
>Why is it teethed like that?
a FIR average filter has a system function that has a sin component with creates the periodicity in the spectrum
H(s) = \frac{\sin (\omega N)}{\omega N} e^{-0.5 s N}
where N is the number of taps in the average filter
Bernd
Thu, 27 Feb 2025 19:27:59 GMT
No. 25525132
>>25525184
>>25525067
do a rectangular filter and show the options pls
also can you select this and show options please?
Bernd
Thu, 27 Feb 2025 19:28:22 GMT
No. 25525137
>>25525203
>>25525092
It's not that simple. Even the best signal generator must be tuned to a signal receiver if you want to maximalize power transfer/minimalize noise.
Everything goes into a billion variables differential equation, and at the end of the day, everything will depend on everything else.
Bernd
Thu, 27 Feb 2025 19:33:31 GMT
No. 25525184
>>25525232
>>25525294
>>25525132
Rectangular and low pass
low pass seems to attack specifically the signal (peaks that go up and down, 4 in the window)
Bernd
Thu, 27 Feb 2025 19:36:22 GMT
No. 25525203
>>25525268
>>25525137
As of now I can only rely on oscilloscope that is part of the amplifier. It has outputs to put a separate oscilloscope in the loop but I dont have it at hand. There is hardware calibration protocol for the amplifier which I did, but I'll see if this "ringing" is an issue, it is worth checking out
Bernd
Thu, 27 Feb 2025 19:39:19 GMT
No. 25525229
>>25525008
ah I didn't know that. then you wouldn't want to do averaging when you're intersted in the signal close to the sampling requency.
Bernd
Thu, 27 Feb 2025 19:39:30 GMT
No. 25525232
>>25525293
>>25525294
>>25525184
yes, the window funciton rectangular basically does an average filtering
this means the peaks in the signal will be "smeared"
you can reduce the peaks futher by using different windows which have even faster declining frequency response, use more terms, or jut reduce first and second band until your output looks fine
for the second one: you dont need to comput this many terms, 16 is fine
reduce the end of passband and lower the stopband (try 100 and 200)
error can be 3 db, but attenuation you can try reducee to 60 dB or 80 dB
post the results
Bernd
Thu, 27 Feb 2025 19:43:08 GMT
No. 25525268
>>25525306
>>25525203
>hardware calibration protocol
Tell us more. This is how riveting the rpi pico api documentation is on the subject. What do you have?
Bernd
Thu, 27 Feb 2025 19:46:51 GMT
No. 25525293
>>25525309
>>25525321
>>25525232
I do want to keep the peaks though, both amplitude and shape. What is between the peaks I want mostly flat
Bernd
Thu, 27 Feb 2025 19:46:54 GMT
No. 25525294
>>25525232
>>25525184
*other windows like kaiser or hann window do not weight all their samples to which the window is applied equally, meaning that effectively your waveform is less "smeared"
also the frequency response for these windows declinnes much faster than for rectangular window (average filter)
you can check the FFT to see the difference for your signal
Bernd
Thu, 27 Feb 2025 19:48:51 GMT
No. 25525306
>>25525268
It's all closed source, hardware calibration in my case means attaching a known value resistor and resistor/capacitor combo to the working end and then waiting 20 minutes.
Bernd
Thu, 27 Feb 2025 19:49:16 GMT
No. 25525309
>>25525344
>>25525293
>I do want to keep the peaks though, both amplitude and shape. What is between the peaks I want mostly flat
then you want the complete opposite of what i thought you want.
can you remove the filters and show the frequency spectrum/FFT again?
chances are you want a band-pass filter
Bernd
Thu, 27 Feb 2025 19:51:15 GMT
No. 25525321
>>25525329
>>25525293
Why don't you post a pic of a noisy signal that's a problem? These are clearly flat enough already that you can easily detect the peaks.
Bernd
Thu, 27 Feb 2025 19:53:08 GMT
No. 25525329
>>25525334
>>25525321
He's the one creating the peaks.
>>25525329
Then I don't understand what he's trying to do. You can just create the peaks without noise.
Bernd
Thu, 27 Feb 2025 19:55:19 GMT
No. 25525338
>>25525334
no the noise seems to come from the system
he wants to attenuate it somehow with a filter
these peaks he creates himself and wants to keep
Bernd
Thu, 27 Feb 2025 19:55:24 GMT
No. 25525339
>>25525347
>>25525383
when you're tallking about picoamps do you think that's thermal noise coming from the resistor and capacitor? that's kinda cool.
Bernd
Thu, 27 Feb 2025 19:56:19 GMT
No. 25525344
>>25525348
>>25525422
>>25525309
I found long duration recording with similar issue and FFT'd it here
>>25524682
High-pass with notch at 50hz worked well for that recording
>>25524762
but not so well for original recording
>>25524829
which is weird
could be all the other settings like term number or what else that I dont know the meaning. Or another noise source. Could be actual biology too, but I'd expect biological noise to have another shape and time constants. Onionbernd mentioned "ringing" and I'll test that when I steal an amplifier from someone
Bernd
Thu, 27 Feb 2025 19:56:33 GMT
No. 25525347
>>25525339
>talking about picoamps
yes this is an insanely weak signal
it has to be thermal noise
Bernd
Thu, 27 Feb 2025 19:57:35 GMT
No. 25525362
>>25525386
>>25525334
He wants to measure something. Maybe he wants more clean samples after the peak. In his current setup he gets only a couple of clean samples after the ramp-up and then the signals quickly peters out to noise.
Bernd
Thu, 27 Feb 2025 20:00:58 GMT
No. 25525383
>>25525413
>>25525339
A high-resistance neuron will have resting membrane currents in order of single picoamps and even femtoamps. Its resolvable with the amplifier that I work with, it amplifies "that".
If hundreds of picoamps are involved then its either not a neuron (could be an astrocyte) or it has a hull breach and it is dying rapidly.
Bernd
Thu, 27 Feb 2025 20:01:18 GMT
No. 25525386
>>25525449
>>25525362
Then it would still help to see an example of the problem.
Bernd
Thu, 27 Feb 2025 20:04:31 GMT
No. 25525413
>>25525383
oh this is more interesting than I initially thought.
Bernd
Thu, 27 Feb 2025 20:05:36 GMT
No. 25525422
>>25525344
could you try out different windowing functions?
the notch filter works well to get rid of the frequency component at 50 Hz
but this component is not the pulse you want to see? for 50 Hz it should be periodic every 20 ms
Bernd
Thu, 27 Feb 2025 20:12:27 GMT
No. 25525483
>>25525570
>>25525449
since these peaks come every 50 ms this means that the frequency of you swapping the voltage has to be at 20 Hz, is this what you configured?
Bernd
Thu, 27 Feb 2025 20:12:48 GMT
No. 25525486
>>25525549
>>25525449
Milli-volts, and pico-amps. You'll pick a butterfly farting in straya.
Which parts of the output signal is interesting to you? The delay between the the input and the output switch? The tail of the decay?
Bernd
Thu, 27 Feb 2025 20:14:24 GMT
No. 25525503
>>25525630
>>25525449
why did you say you were happy with the notch filter? it completely removed the peaks you wanted to see, no?
>>25524762
this is confusing
Bernd
Thu, 27 Feb 2025 20:14:30 GMT
No. 25525505
>>25525640
>>25525449
And then you're measuring the peaks? That should be easy enough here. You said sometimes you're getting noise that's a problem:
>>25524130 but you never posted an example of it.
>>25525486
Going to a better example of filtering goal, above is the issue I have with the baseline, with possibly a signal in the middle. Below is filtering result using a 50hz notch filter in this threada. Signal is still there but to left and right of it seems to be newly-created artifacts.
Bernd
Thu, 27 Feb 2025 20:23:40 GMT
No. 25525570
>>25525483
Its a repeating pattern, 10ms holding voltage, 50ms square step to +10mV relative to holding, then back to 40ms of holding voltage. A square step. Repeated 10 times without gaps.
Bernd
Thu, 27 Feb 2025 20:24:01 GMT
No. 25525574
>>25525549
a notch filter wont fix this
can you try different window filters and see if they fix it?
Bernd
Thu, 27 Feb 2025 20:25:47 GMT
No. 25525594
Does bernd know about liftering?
Bernd
Thu, 27 Feb 2025 20:26:12 GMT
No. 25525599
>>25525549
in this plot the signal being evened out comes from the high pass filter
is this more what you are looking for?
if you dont want the artifacts then make it just a high pass
Bernd
Thu, 27 Feb 2025 20:30:00 GMT
No. 25525630
>>25525644
>>25525503
It didnt
>>25524829 they were just offset. I have two datasets in this thread, one short with peaks, about 1s, another long without peaks, about 30s. Short one did not work well with the fourier transform, because it was short. But longer one did work. They both experienced same kind of interference at the time of recording. Different sampling rate though... actually sampling rate might be relevant here, because I may be applying same filter but the tool expects same sampling rate for different recordings. The one with the peak is some weird ass number like 6.03fuck khz or something, I dont remember. That might explain why filter isnt good looking, I put 20khz for both
Bernd
Thu, 27 Feb 2025 20:31:39 GMT
No. 25525644
>>25525662
>>25525630
>Different sampling rate though
yes, this is likely the issue
if you fit a filter for a signal that is for one sample rate then the filter wont work for a signal with a different sample rate
Bernd
Thu, 27 Feb 2025 20:31:47 GMT
No. 25525645
>>25525549
This picture clarifies the ringing somewhat. It's not. The noise looks the same near and far away from the signal.
I would check it anyway.
Bernd
Thu, 27 Feb 2025 20:35:07 GMT
No. 25525662
>>25525644
I just remembered it now. The protocol with peaks is really really legacy stuff from different era, different hardware, different country even, its around because I have a nice analysis tool written for this specific sampling rate. I really should get rid of it, or rewrite it maybe. But it also works, so maybe I sneed it
Bernd
Thu, 27 Feb 2025 21:44:34 GMT
No. 25526064
After fucking around and seeing that sampling rate wasnt the core issue I feel IIR filters is where the solution is at. But its even more complex and I'm fully spent now
Thx bern fun was had